Answers

Lo cual can only be used to refer to something that has already been mentioned in the same sentence, but doesn't have a gender or number, so the neuter pronoun is preferred.

Hay un libro nuevo por Isabel Allende, lo cual me encanta.

Lo que can be used any time lo cual is used except that it can also be used to refer to something that has not been brought up before in the same sentence. It can also be used at the beginning of a sentence.